ksmbd: fix use-after-free in __smb2_lease_break_noti()

Move tcp_transport free to ksmbd_conn_free. If ksmbd connection is
referenced when ksmbd server thread terminates, It will not be freed,
but conn->tcp_transport is freed. __smb2_lease_break_noti can be performed
asynchronously when the connection is disconnected. __smb2_lease_break_noti
calls ksmbd_conn_write, which can cause use-after-free
when conn->ksmbd_transport is already freed.

Cc: [e-mail]
Reported-by: Norbert Szetei <[e-mail]>
Tested-by: Norbert Szetei <[e-mail]>
Signed-off-by: Namjae Jeon <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/smb/server/connection.c

···
 	xa_destroy(&conn->sessions);
 	kvfree(conn->request_buf);
 	kfree(conn->preauth_info);
-	if (atomic_dec_and_test(&conn->refcnt))
+	if (atomic_dec_and_test(&conn->refcnt)) {
+		ksmbd_free_transport(conn->transport);
 		kfree(conn);
+	}
 }
 
 /**

fs/smb/server/transport_tcp.c

···
 	return t;
 }
 
+void ksmbd_free_transport(struct ksmbd_transport *kt)
+{
+	struct tcp_transport *t = TCP_TRANS(kt);
+
+	sock_release(t->sock);
+	kfree(t->iov);
+	kfree(t);
+}
+
 static void free_transport(struct tcp_transport *t)
 {
 	kernel_sock_shutdown(t->sock, SHUT_RDWR);
-	sock_release(t->sock);
-	t->sock = NULL;
-
 	ksmbd_conn_free(KSMBD_TRANS(t)->conn);
-	kfree(t->iov);
-	kfree(t);
 }
 
 /**

fs/smb/server/transport_tcp.h

···
 
 int ksmbd_tcp_set_interfaces(char *ifc_list, int ifc_list_sz);
 struct interface *ksmbd_find_netdev_name_iface_list(char *netdev_name);
+void ksmbd_free_transport(struct ksmbd_transport *kt);
 int ksmbd_tcp_init(void);
 void ksmbd_tcp_destroy(void);